Fish Size Research Articles

Recreational Anglers’ Specialization and Perception of Management Measures in Yucatan, Mexico

ABSTRACT Understanding anglers’ diversity can help to improve the effectiveness of governing recreational fisheries. Online and in situ surveys were applied to evaluate perceptions and preferences among anglers’ fishing frequency (occasional, regular, and frequent) as an indicator of their specialization in Yucatan, Mexico. Occasional anglers’ most reported fish species are associated with bottom fishing (non-selective), while regular and frequent with trolling and casting (selective). The primary fate of the catches was to preserve the sizes they considered large enough and release the small ones. Unlike occasional, the frequent does not consider overexploited species to be affected by this fishery. The fish size regulation was chosen as the most effective management measure among anglers of all specialization levels. The social and ecological context of the Yucatecan coast must be considered before introducing management measures, and resource managers must establish collaboration strategies with the most specialized anglers to promote best fishing practices.

Managing the Dissolved Oxygen Balance of Open Atlantic Salmon Sea Cages: A Narrative Review

ABSTRACTAs Atlantic salmon depend on dissolved oxygen (DO) to survive and grow, managing DO is essential for welfare and growth. However, the dynamics of DO in the open sea cages are complex, caused by a range of factors that interact and create compounding effects. To understand DO dynamics, two pillars of knowledge are essential: the supply of DO to the cages and the consumption of DO in the cages. The components of these two pillars vary greatly across both time and space, with factors including ambient sea temperature and current, density stratification, fish size, health and metabolism, biomass density and distribution, topography, production routines and farm configuration. In the production environment, these factors often interact, making related analyses on effects, causality and effective management highly challenging. Exacerbating matters, existing knowledge is fragmented across multiple disciplines, making it challenging for end‐users to access. Using sensors is often necessary to understand and manage the complexity of DO, and the interest to implement digital technologies to aquaculture operations and utilize big data analyses is growing, but to succeed in the application, an in‐depth understanding of the relevant dynamics is necessary. Consequently, this review is produced to compile existing knowledge on the many factors that influence the consumption or supply of DO in the sea cages, and their relationship to each other. In this narrative review, we explore the known interactions and compounding effects between these factors, and synthesize it in a causal diagram for holistic analyses of the DO balance.

Environmental and Spatial Effects on Co‐Occurrence Network Size and Taxonomic Similarity in Stream Diatoms, Insects and Fish

ABSTRACTAimThe influences of environmental and spatial processes on species composition have been at the center of metacommunity ecology. Conversely, the relative importance of these processes for species co‐occurrences and taxonomic similarity has remained poorly understood. We hypothesised that at a subcontinental scale, shared environmental preference would be the major driver of co‐occurrences across species groups. In contrast, co‐occurrences due to shared dispersal history were more likely in dispersal‐limited taxa. Finally, we tested whether taxa co‐occurring due to similar responses to environmental and spatial processes were more taxonomically similar than expected by chance.LocationThe conterminous United States.Time Period1993–2019.Major Taxa StudiedStream diatoms, insects and fish.MethodsWe generated co‐occurrence networks and developed methodology to determine the proportions of nodes and edges explained by pure environment alone (after accounting for space), pure space alone (after accounting for the environment), pure environment and pure space together, and spatially structured environment. Taxonomic similarity of taxa co‐occurring because of environmental and/or spatial controls or because of unmeasured processes was compared to that of a null model.ResultsPure environment alone, spatially structured environment, and pure environment and pure space together explained the greatest proportion of nodes and edges in the co‐occurrence networks of diatom species and genera, and insect genera. Conversely, pure environment and pure space together best explained the nodes and edges in the co‐occurrence network of fish species and genera. Co‐occurring taxa were more closely related than the random expectation in all comparisons.Main ConclusionsThe environment controlled co‐occurrences in all groups, while the influence of space was the strongest in fish, the most dispersal‐limited group in our study. All co‐occurring taxa were more taxonomically related than expected by chance due to environmental or spatial overlap or unaccounted factors.

Elemental Distribution in Tissues of Shorthorn Sculpins (Myoxocephalus scorpius) from Kongsfjorden in Svalbard

The shorthorn sculpin (Myoxocephalus scorpius) is considered a suitable sentinel species for marine pollution in the Arctic due to its ecology and stationary habits. To evaluate its role as a bioindicator for potential natural and anthropic impacts on the marine ecosystem of the Kongsfjorden (Svalbard, Norwegian Arctic), 33 female and male specimens of shorthorn sculpins were collected in July 2018 in proximity of the Ny-Ålesund international research facility and analyzed for the content of 25 major and trace elements and methylmercury (MeHg) in the muscle, liver, gonads, and gills by using spectroscopic techniques. Most elements had their maximum average concentrations in the gills (Al, Cr, Fe, Mn, Na, Ni, Pb, Se, Si, Sr, and V), while the livers featured higher contents of some toxic and heavy metals (As, Cd, Cu, Mo, and Zn). The muscle was characterized by high contents of Ca, K, and Mg, while Ba, Co, and P were mostly concentrated in the gonads. The gonads presented higher concentrations of Cr, K, Mg, Ni, P, and V for the males and Co, Cu, Fe, Mn, and Se for the females. Both the total Hg and MeHg concentrations in the muscle correlated with the fish size, indicating bioaccumulation, although high Se/Hg molar ratios (11.0 ± 2.2) suggested a low toxic potential of mercury.

Marine protection and environmental forcing influence fish‐derived nutrient cycling in kelp forests

Abstract Animal consumers excrete dissolved inorganic nitrogen, an essential nutrient for regulating primary production and macroalgal growth in the ocean. Often overlooked in attempts to explain kelp forest productivity, relatively little is known about the role of consumers in nutrient cycling in temperate systems, such as the magnitude of nutrients excreted and the factors that influence spatial and temporal variability in consumer‐derived nutrients. To investigate the supply of ammonium (NH4+) excreted by the dominant members of the nearshore rocky reef fish community, we combined empirically‐measured relationships between excretion rate and body mass with data on fish density and size structure from visual SCUBA surveys conducted from 2005 to 2018 in the northern Channel Islands, California, USA. The fish community excreted a substantial amount of ammonium to the kelp forest (mean: 95.5–131.3 μmol·m−2·h−1), however excretion varied substantially among sites and over time (range: 23.1–247.9 μmol·m−2·h−1). The ammonium supply was influenced by the establishment of marine protected areas (MPAs) that restricted fishing activities and environmental characteristics that influenced geographic and temporal shifts in the overarching fish community structure. Fish‐derived ammonium excretion rates were 50%–80% greater inside MPAs compared to areas open to fishing, while environmental and habitat characteristics (e.g. habitat vertical relief, kelp biomass, wave exposure, chlorophyll a) explained 85% of the spatial variation in community excretion rates. In contrast, large‐scale oceanographic phenomena (e.g. North Pacific Gyre Oscillation index) and past patterns of fish recruitment explained 57% of the temporal variation in nutrient excretion over the 14‐year time series. Results suggest that fish‐derived ammonium may provide an important and underappreciated nutrient source to kelp beds, particularly during low‐nutrient periods (e.g. seasonal reductions in upwelling or El Niño‐Southern Oscillation events), and that fishing disrupts these nutrient cycling pathways. Fishes likely play a critical role in supporting the resiliency of kelp forest ecosystems by supplying a relatively constant source of reduced nitrogen that can be utilized by giant kelp and other macroalgae to fuel primary production of biogenic habitat. Read the free Plain Language Summary for this article on the Journal blog.

A transferable approach for quantifying benthic fish sizes and densities in annotated underwater images

Abstract Benthic fishes are a common target of scientific monitoring but are difficult to quantify because of their close association to bottom habitats that are hard to access. Advances in image‐acquisition technologies, machine vision and deep learning have made capturing and quantifying fishes with cameras increasingly feasible. We present a method and open‐source software called ‘FishScale’ to estimate benthic fish lengths, numeric abundance and biomass density in underwater environments assessed with down‐looking monocular images. ‘FishScale’ estimates fish abundances and size frequencies from near‐nadir monocular images where fish have already been semantically segmented. The software accounts for lens distortion, underwater magnification effects and fish body curvature to automatically estimate fish lengths and the areas of images where they were captured. Numeric and biomass density are estimated through a deterministic machine vision algorithm that requires a user‐provided length‐weight relationship for species of interest and calibration images. Results from validation studies show that lengths and weights can be estimated with high accuracy and precision for round goby (Neogobius melanostomus) captured in distorted action camera images, and from large‐bodied lake trout (Salvelinus namaycush) imaged with a machine vision camera. The real‐world utility of the approach is demonstrated in a case study estimating round goby abundances and size frequencies along a 10.7‐km transect surveyed with an autonomous underwater vehicle in Lake Michigan, USA. Our validation studies demonstrate that the approach estimates benthic and benthopelagic fish lengths and weights with little bias and good accuracy and precision for species with much different body shapes and sizes. The method is applicable to data collected using a variety of nadir imaging approaches with widespread applications to fisheries monitoring and quantification of any species or object for which nadir images and working distances between the camera and feature of interest are available.

Spawning aggregation of blacktail snapper (Lutjanus fulvus) in an okinawan coral reef: lunar-phase periodicity of aggregation formation, seasonal consistency in fish spatial distribution, and fish size and age frequency in the aggregation site

Spawning aggregation of blacktail snapper (Lutjanus fulvus) in an okinawan coral reef: lunar-phase periodicity of aggregation formation, seasonal consistency in fish spatial distribution, and fish size and age frequency in the aggregation site

Accounting for Salmon Body Size Declines in Fishery Management Can Reduce Conservation Risks

ABSTRACTChanges in population demographic structure can have tangible but unknown effects on management effectiveness. Fishery management of Pacific salmon is often informed by estimates of the number of spawners expected to produce maximum sustainable yield (SMSY), implicitly assuming that reproductive output per spawner does not change over time. However, many salmon populations have experienced long‐term trends in age, sex and length compositions that have resulted in smaller body sizes of mature fish. We present an empirically based simulation approach for evaluating management implications of declining reproductive output resulting from shifting demographics. We simulated populations with or without demographic trends, selective or unselective harvests, and harvest policies based on assessment methods that did or did not account explicitly for demographic trends when estimating SMSY. A management strategy evaluation showed reduced expected harvests and run sizes when populations exhibited negative demographic trends. Reduced abundances and increased conservation risks (higher probability of falling below an abundance threshold) could be partially mitigated by using stock‐recruitment analyses based on total egg mass instead of spawner abundance, or via precautionary management where target escapements were higher than SMSY, especially in fisheries that selectively removed large fish. Explicit accounting of demographic trends in stock‐recruit analyses resulted in up to 25% higher run sizes and up to 20% lower conservation risks compared to traditional methods when trends toward smaller, younger and male‐biased runs were present in the population. Conservation of population demographic structure may be critical for sustaining productive fish populations and their benefits to ecosystems and people.

The Effect of Season and The Implications For Sustainable Fisheries on The Catch Results of Yellowfin Tuna In Indonesia

This study assessed the purse seine, handline and pole and line catches at PPS (Samudera Fishing Port Kendari) specifically targeting skipjack and yellowfin tuna in the Banda Sea. Although there has been a rise in tuna output over the past two years, the examination of fish size in September until November revealed substantial fluctuation. Additionally, the implementation of the moratorium policy had a detrimental effect. Ensuring the sustainability of fisheries in the Banda Sea, particularly for large pelagic fish like skipjack and yellowfin tuna, necessitates the implementation of adaptive management and selective fishing practices, with a particular focus on enforcing mesh size regulations. The aims of this study were to examine the patterns of tuna fisheries landing at PPS, specifically focusing on the sorts of catches made using purse seine, handline, and pole and line fishing methods. Additionally, the study aimed to assess the length frequency distribution of Thunnus albacares caught using purse seine, handline, and pole and line fishing gear. The methodology offers a thorough framework for eval_uating the sustainability of Thunnus albacares fisheries in PPS Kendari. Policymakers can develop effective management plans for long-term resource sustainability by assessing catch composition, productivity, and size distribution across various fishing gears. The analysis of this study conducted in September - November 2023 revealed that the fish catches varied in size, ranging from 13 cmFL to 124 cmFL.

Host-Parasite Interaction Between the Nematoda Procamallanus (Spirocamallanus) paraensis and Fish Hoplias malabaricus From the Natural Environment in the Brazilian Amazon.

Histopathological studies of parasitic infections in fish from the natural environment of Brazilian Amazon, are quite scarce. In this study, we investigated the histopathological changes of the proximal intestine of specimens of the Amazonian fish Hoplias malabaricus infected by the hematophagous nematode Procamallanus (Spirocamallanus) paraensis. The prevalence of the infection was 60%, with an average abundance of 1.46 and an average intensity of 2.43 parasites/fish. No significant difference was observed in the prevalence of infection and fish size or sex, but larger fish showed greater infection intensity, which was also significantly higher in male hosts. Histological sections of the proximal intestine showed reduction and loss of the epithelial lining, exposure of the lamina propria where the nematode interacts with the intestine wall, through the insertion of the buccal capsule and fish cellular debris in the intestinal lumen. In addition, areas with bleeding and inflammatory infiltrate were observed, but no changes or presence of parasite structures were observed in the other tunics of the intestinal wall.

Effect of fish consumption on the interactions between the gut microbiota and inflammatory markers: Results from the iFISH study

Dietary intake can influence immune function indirectly by affecting the gut microbiota composition and metabolism(1). Fish consumption has been shown to positively regulate the gut microbiota in humans(2,3);albeit in those studies fish was consumed in high amounts (500-750g/week) and immune function was not investigated. This study investigated the effect of consuming the UK dietary recommendation for fish(4) (2 portions [140-280g/week], one of which is oily) on the gut microbiota alpha diversity. Further, we examined if changes (pre- to post-intervention) in the gut microbiota composition were associated with changes in immune cytokine concentrations.An 8-week randomised controlled trial in low fish consuming women of childbearing age (n = 41; median age 23y) investigated the effect of consuming 1 or 2 portions of fish (tuna or sardines)/week compared to not consuming fish. A blood sample was collected to measure inflammatory cytokines (tumour necrosis factor-a, interleukin [IL]-1b, IL-5, IL-6, IL-17A and IL-22) pre-and post-intervention. Faecal samples were collected at both timepoints and extracted DNA was used to determine gut microbiota compositional profiles using 16S metagenomic sequencing (Illumina, USA). Statistical analysis investigated significant differences in changes in gut microbiota alpha diversity and compositional relative abundances between fish intervention (N = 26) and control (N = 15), then secondary analysis stratified by portion size (1 vs 2 portions) and type of fish (tuna vs sardines). Differences in cytokines between fish intervention and control were assessed by Mann-Whitney U. Spearman rank coefficient assessed associations between the changes in gut microbiota relative abundances with cytokine changes in fish and control groups.Fish consumption increased gut microbiota alpha diversity indices (Chao1 [7.37 ± 41.23], Simpson [0.003 ± 0.163], Shannon [0.07 ± 0.33], phylogenetic diversity [0.35 ± 2.59], observed species [9.00 ± 40.06]), albeit this was not significant compared to the control group (p>0.05). Consumption of fish, specifically sardines, for 8 weeks significantly reduced Bacteroidetes (-4.77 ± 4.88%) when compared to control (+4.15 ± 7.58%) (p<0.01). No significant differences were observed between the change in relative abundances of gut microbiota at genus-level taxa or inflammatory cytokines between the fish intervention and control. In the fish intervention group, increases in IL-17A, IL-22 and IL-6 concentrations were positively correlated with changes in Alistipes, Rhodococcus, Haemophilus, Barnesiella and Akkermansia relative abundances (p<0.05).Although not statistically significant, consistent findings suggest that fish intake, in line with dietary guidelines, may have favourable impact on gut microbiota. Sardines, oily fish rich in n-3 polyunsaturated fatty acids, may have health benefits in disease states where Bacteroidetes is elevated; nevertheless, further research is required in a larger cohort over a longer period.

Automation System of Water Circulation and Fish Feeding in Tilapia Fish Pond with Solar Panel Source

Tilapia cultivation requires good management of water quality and proper feeding to ensure optimal fish growth. One of the main challenges in this process is maintaining the water pH level within ideal limits and providing feed according to the needs of the fish based on their size. In addition, limited access to electricity in some locations makes fish pond management less efficient. This study aims to design an automated water circulation system that is regulated based on the water pH level and automatic feeding according to the needs of the fish, by utilizing solar panels as a power source. This system uses a pH sensor to monitor water conditions in real time and regulate water circulation to maintain ideal pH levels. Feeding is regulated based on the size and number of fish to ensure optimal feed efficiency and fish growth. This system is powered by solar panel energy, so it can operate independently without relying on conventional electricity networks. Test results show that the system is able to maintain water pH stability and automate feeding with high accuracy, while utilizing renewable energy effectively. The use of solar panels not only reduces dependence on electricity, but also reduces operational costs and supports environmental sustainability. This system is expected to increase the efficiency and productivity of tilapia cultivation, especially in areas with limited access to electricity.

Impact of Climate Deviation on Reproductive Profile of Nile Tilapia, Oreochromis niloticus (Linnaeus, 1758) from the Tons River, India

Nile tilapia, Oreochromis niloticus is among the leading farmed species around the world as well as a powerful invader in many countries globally. Studies were undertaken during the period from February 2019 to January 2020 from the lower stretch of the Tons River at Prayagraj, Uttar Pradesh, India. During the sampling period, 683 fish specimens of Nile Tilapia, Oreochromis niloticus (336 males and 347 females) were collected and studied for evaluation of sex ratio and sex structure. The sex ratios of male and female fishes were very close and reported 1.0:1.03 in the stock. The male ratio was higher in the small size group of fish with 81 to 200 mm size groups and 411 to 470 mm size group. The sex structure of males and females was observed at 49.19% and 50.81%, respectively in the case of stock. The female proportion was recorded as a minimum with 37.50% in the 441-470 cm size group and highest with 54.84% in the 381-410 mm size group. However, the male proportion was reported lowest at 45.16% in the 381-410 mm size group and highest at 62.50% in the 441-470 mm size group. In the present findings, O. niloticus was found to reach maturity starting below 138 mm of total length, taking individual fish. The fishes breed in the months of March to June and September to November of the year. The number of eggs per individual ranged from 393 to 4338 in the size of fish varied from 138-452 mm. The reported fecundity and sex ratio of O. niloticus indicated that the climatic condition or environmental condition of the Tons River was most suitable. The environmental condition (especially temperature) of the Tons River at Prayagraj is slightly warm compared to the Ganga River which is very favourable for O. niloticus. The water current velocity of the Tons River is very poor. Both parameters are very helpful for the stability of O. niloticus in the Tons River at Prayagraj. The high fecundity of O. niloticus in the Tons River at Prayagraj could probably be a result of a combination of different causes such as climatic conditions, habitat structure, food abundance, water quality, and quality of food. Therefore, the present study aimed to update the information on the sex ratio, sex structure, and fecundity of O. niloticus with respect to climate from the Tons River, India.

Factors Influencing the Prevalence of Hyperpigmented Melanistic Lesions in Smallmouth Bass Micropterus dolomieu in the Susquehanna River Basin, Pennsylvania.

Hyperpigmented melanistic lesions (HPMLs) are a visual anomaly documented on the skin of smallmouth bass Micropterus dolomieu in the Susquehanna River Basin, Pennsylvania and in numerous other geographical locations. Currently, there is a lack of information on environmental and fish characteristics that may influence the prevalence of HPMLs associated with a recently described Adomavirus. The goal of this study was to understand potential drivers associated with HPMLs in socioeconomically and ecologically important riverine smallmouth bass populations. A total of 16,220 smallmouth bass were collected and examined for HPMLs between 2012 and 2022 in the Susquehanna River Basin. Overall, HPMLs were documented on 2.9% of fish collected. The interaction between temperature and fish size suggested differing relationships between shorter and longer fish with respect to temperature. Predicted probability of HPML prevalence ranged from 1.1% (95% CI = 0.3, 3.2) at 4°C to 0.01% (CI = 0.00, 0.04) at 26°C for an age-0 (125 mm) fish. In contrast, predicted probability of HPML prevalence ranged from 10.5% (95% CI = 5.8, 18.9) at 4°C to 0.8% (CI = 0.4, 1.5) at 26°C for an adult (322 mm) fish. Overall, HPMLs were more common in longer fish during cooler temperature periods which also corresponds to key life history periods for smallmouth bass (e.g., pre-spawn and overwintering) and could represent different exposure histories for juvenile and adult fish.

Condition states in anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) revealed by energy and proximate composition relationships.

Energy content has long been proposed as a fundamental, integrated, and reliable indicator of the condition of individuals as it reflects past bioenergetics and influences future life-history traits. There is a direct biochemical link between energy density and body composition described by four main compounds in fish (protein, lipid, ash, and water), with proteins and lipids being the sources of energy. If relationships between water content, or lipid content, and energy density have been well described in relative terms, the absolute mass variations in the proximate composition have been overlooked and thus their interpretation is often equivocal. In our study, based on a large and unique dataset on the proximate composition and energy density of anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) from sampling in the Bay of Biscay and the English Channel, we aimed to better explain the patterns between water content and other proximate components or energy density, based on the dynamics of proteins, lipids, and water absolute masses. For the first time, we defined good, intermediate, and poor condition states in wild fish, based on water content, corresponding to the different dynamics of lipids and proteins in the metabolism of individuals. Anchovy and sardine exhibited remarkably similar patterns of variation in the compounds and in the limits between the condition states with respect to water content. Those patterns revealed that water mass remained constant for a given fish size whatever its condition state, and that variability in water content only resulted from the variation in lipid and protein masses. Furthermore, the differential dynamics of proteins and lipids, with only lipids mobilized in the good condition state, only proteins in the poor condition state, and both proteins and lipids in the intermediate condition state, elucidates the nonlinear pattern observed in the relationship between energy density and water content. Overall, our results highlight the importance of monitoring the intraspecific variations in water content to predict the proximate composition and energy content in small pelagic fish and better assess individual and population conditions in changing ecosystems as well as to better parameterize bioenergetic models.

A guide to the otoliths of Southern Ocean lanternfishes (Myctophidae)

In the Southern Ocean, myctophids (family Myctophidae) are speciose, dominate the mesopelagic fish biomass, and are important in the diets of many fishes, squids, seabirds, and marine mammals. Consequently, they play a key role in carbon export and energy transfer from primary consumers to top predators. However, they are delicate and rarely found intact in predator stomachs, which makes them difficult to identify to species. Fortunately, their otoliths (sagittae) are mostly distinctive and therefore useful for species identification. Previous studies describing Southern Ocean myctophid otoliths were often limited by small sample sizes or focused on only a few species. To facilitate myctophid identifications in diet studies, we provide scanning electron microscope images of otoliths with brief descriptions for 37 species of Southern Ocean myctophids. The identities of problematic taxa were confirmed with DNA. Most species were found to have distinctive otoliths, which can be used to identify them to the species level. Large Gymnoscopelus piabilis otoliths comprised two types, which may represent different species. In addition, allometric equations are provided for 32 species to enable back calculation of fish size.

Coordination of energy loss and fish friendliness for a low-head tubular-pump blade based on a multi-objective optimization model

Tubular pumps and turbines are the water-to-electricity conversion devices widely used in pumped hydro storage systems for low heads and high flow rates. An ecological concern is the high proportion of fish injuries caused by the rotating blades. In this study, a tubular pump blade is retrofitted to balance the energy loss and fish friendliness through multi-objective optimization, combining computational fluid dynamics with a mathematical blade strike model. Sensitivity analysis identifies nine geometric variables out of thirteen for optimizing blade design. An approximation model is developed to implement optimization algorithm and achieve the objective function. By artificially assigning weights to targeted performance metrics, three scenarios are obtained: the optimal efficiency scheme (A), the optimal fish friendliness scheme (C) and the balanced scheme (B). Scheme C achieves a fish survival ratio of 100 % at multiple flow rates (for fish lengths of Lf/D=1/12), but results in a 6.4 % decrease in efficiency compared to scheme A. Additionally, a negative blade attack angle can improve flow pattern. Considerable reduction in fish mortality can be obtained by equipping the rotor with a larger size but lower shaft speed, while also limiting the fish size to pass through the pump running at a reduced flow rate.

Pervasive Microplastic Ingestion by Commercial Fish Species from a Natural Lagoon Environment

Microplastics have emerged as a significant global environmental concern in the recent decade. The aim of this study was to elucidate microplastic contamination of commercial fish species in a natural lagoon environment. Microplastic contamination was examined in the gastrointestinal tracts and gills of 157 commercial fish from 18 species with varying feeding habits in a vital and sensitive lagoon ecosystem, which connects to the Indian ocean. Microplastics were extracted using digestion, followed by stereomicroscopic inspection using Nile Red stain, and identified via μ-FTIR analysis. Over half of studied fishes ingested microplastics (54.14%). Filaments (50%) and blue items (43%) were the most commonly ingested. Of all the fish species, Eubleekeria splendens had the highest average concentration of microplastics in GIT (1.41 ± 2.52 items/g w.w. tissues), although no statistically significant difference in amount of ingested microplastics (items/g w.w. tissues) was observed among species. The highest concentrations of inhaled microplastics were recorded in Sillago vincenti (1.38 ± 1.30 items/g w.w. tissues). The majority of the extracted microplastics (33%) belonged in the size class 500–1500 μm with rayon, polyethylene terephthalate, and polypropylene as the primary polymers. This study found no correlation between microplastic ingestion and fish species and feeding habits, but a positive correlation with fish size was observed. These findings reveal widespread microplastic contamination in edible fish, posing potential risks to commercially important species due to increasing pollution in lagoon ecosystems.

Morphofunctional characterization of the three main adipose tissue depots in rainbow trout (Oncorhynchus mykiss)

Visceral adipose tissue (VAT) is the primary fat reservoir and energy source in fish. Other relevant fat depots include subcutaneous adipose tissue (SAT), located under epithelial layers, and intramuscular adipose tissue (IMAT), found between the myotomes. The present study investigates the morphological, gene expression and functional characteristics of these different depots in rainbow trout (Oncorhynchus mykiss). Commercial rainbow trout of two different average weights were sampled for histology, lipid quantification and fatty acids profile. Mature adipocytes were isolated for gene expression analyses of lipid metabolic markers. Both VAT and SAT showed large adipocytes, and high total lipid content, suggesting hypertrophic growth. Adipocytes in IMAT were consistently smaller regardless of fish size. While fatty acid composition was similar across depots, SAT had lower levels of palmitic acid and higher levels of polyunsaturated fatty acids that act as precursors of phospholipids and eicosanoids such as eicosapentaenoic acid, compared to VAT and IMAT. Gene expression analyses revealed higher levels of fatty acid transporters, lipolysis and β-oxidation markers in VAT and SAT compared to IMAT, suggesting a more active lipid metabolism. These data support the role of VAT as the main energy depot, while SAT may act as a secondary reservoir, and IMAT potentially serves as an occasional energy source for muscles. This study provides valuable insights into the distinct properties of the different fat depots in fish, which may help to optimize strategies to modulate adiposity for improved health, metabolism, and product quality.

Bioaccumulation, contamination and health risks of trace elements in wild fish in Chongqing City, China: a consumer guidance regarding fish size.

Trace elements generally contaminate wild fish, particularly in megacities, necessitating guided consumption practices. This study investigated the bioaccumulation of trace elements in wild fish from Chongqing City in June 2021. We evaluated their contamination and associated health risks to establish consumption guidance based on fish size. Our results indicate that the concentrations of Zn, Pb, Cr, and As were relatively high, with some fish exceeding the maximum residue limits. Herbivorous and pelagic fish generally exhibited lower bioaccumulation of most trace elements, except for Cr and As, which were higher in pelagic species. The contamination indices (Pi) for Cr, Pb and As were consistently above 0.2, indicating widespread contamination. The most contaminated fish typically measured around 19cm in length and weighed approximately 90g. Only the maximum target hazard quotients (THQ) for As, Cr, and Hg exceeded 1, with a notably high ratio of THQ(As) > 1, highlighting concerns over arsenic contamination. The THQ(As) remained below 1 for adults across all fish species, whereas for children, species such as Onychostoma sima, Pseudohemiculter dispar, and Parabramis pekinensis exceeded this threshold. Fish safe for adult consumption generally measured 13cm in length and weighed 20g, and for children, 16cm and 25g. Consequently, selecting larger fish is likely to reduce the consumption of contaminated fish, thereby decreasing health risks to the public. The centralization of contaminated fish with high risk in specific size range confirmed fish size could be used to gauge the contamination and health risk of fish.